The November 7-8, 2011 Severe Weather Event

Photo courtesy of Dustin Wilcox.
A Large Tornado moves over Saddle Mountain.

Photo courtesy of Steve Grabman.
Tornado near Tipton, OK.

Radar Reflectivity of a tornado-producing
supercell south of Tipton, OK

Radar Velocity of a tornado-producing
supercell south of Tipton, OK

Radar Reflectivity/Velocity of a
tornado-producing supercell
northwest of Meers, OK

A powerful storm system moving through the southern Great Plains produced tornadoes, large hail, damaging winds and flooding across parts of Oklahoma and western north Texas on November 7-8, 2011.

The system initially produced numerous thunderstorms, heavy rainfall and flash flooding over parts of south central Oklahoma during the late evening of November 6th and early morning of November 7th. Rainfall totals of 5-9 inches were reported across parts of Jefferson, Carter and Murray counties.

The system then generated severe weather including tornadoes, large hail, damaging winds and flooding from the early afternoon of November 7th through the early morning of November 8th. Several supercell thunderstorms developed over southwest Oklahoma during the mid-afternoon hours and moved northeast. One particularly nasty supercell thunderstorm developed over northern Wilbarger county in north Texas. This thunderstorm moved northeast into Tillman county, eventually producing at least six tornadoes over a five county area. If you would like to view images of the November 7, 2011 tornadoes, go to the Storm Multimedia web page. A preliminary tornado track map is also available below.

Two of the tornadoes moved near two Oklahoma Mesonet sites, both taking direct hits. The Mesonet site at Tipton measured 86.4 mph before it was destroyed. The Mesonet site near Fort Cobb measured 91.4 mph before it was destroyed. Both sites also recorded significant drops in surface pressure. You can see the recorded data (before malfunctioning) at Tipton and Fort Cobb, courtesy of the Oklahoma Mesonet.

Other supercells over southwest Oklahoma eventually congealed into a complex of storms and moved east into central Oklahoma. Numerous reports of high winds (92 mph near Clinton, OK) and hail up to golf ball-size were reported. The Storm Prediction Center has put together a web site that lets you look at the weather setup before and during the event (i.e. upper-level wind data, skew T / log P diagrams, etc.). You can view that data by clicking here.

Additionally, the thunderstorms dropped heavy rainfall across parts of central Oklahoma including the OKC metro area. Rainfall totals of 4-7 inches produced significant runoff and flash flooding in this area. Some creeks and streams in northwestern Oklahoma County and southern Logan County, including Deer Creek, Bluff Creek and Cottonwood Creek, flooded on November 8th and closed local roads and lowlands. The floodwaters eventually moved downstream through Cottonwood Creek and produced flooding or near bankfull conditions near the Seward and Guthrie areas through the early morning hours of November 9th. Significant within-bank rises also occurred along the North Canadian River in Canadian County, and the Canadian River near Bridgeport, OK.

Unrelated to the weather, but adding to the mayhem of the day, a magnitude 4.7 earthquake shook many residents of Oklahoma. Many of those affected were in the midst of the severe weather event. This is not to be confused with the earthquake that was recorded just two days before (magitude 5.6), or the earthquake recorded the night before that (magnitude 4.7).